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Forum:DNA in bones
A critic on the Fossil Forum told me this about Schweitzer's DNA discovery: "The reason Schweitzer argues the DNA she found isn't bacterial has nothing to do with cell membranes (which bacteria have by the way), instead it has to do with a completely different test she ran where she used an antibody specific to histones to stain her samples. Histones are used by eukaryotic cells to package DNA tightly into a chromosome. Bacteria do not use histones to package DNA. Schweitzer found that her samples all tested positive for histones, which looks pretty good ... except. It's true that bacteria do not use histones, but archaea do :). Archaea utilize histones very similarly to the way we do, to help package DNA. Archaea were once thought of strictly as extremophiles, but this has since been disproved. Archaea are found pretty much everywhere, in the soil, in the middle of rocks, in the ocean, in our gut biota, even in the air we breath. Of particular note are the methanogenic archaea which are intimately associated with decay ... you know, like a dead dinosaur." Jurassic Park Treasury (talk) 05:40, September 13, 2013 (UTC) :Do Archaea have osteocytes too......... No, they haven't. The proteins were inside those osteocytes (if I remember correctly). The Histone 4 sequence doesn't match with any histones when I blasted it. The best match I could find within 5 minutes was the protein cobaltochelatase in Methanococcus maripaludis (Maybe you could run this test again): Dinosaur: DAVTYTEHAK M. maripaludis Dino 5 YTEHAK 10 (numbers show the positions of amino acids in protein) Archaea 329 YTEHAK 334 Dino 1 DAVT 4 Archaea 970 DAVT 973 The dinosaurs and Archaea probably got this code from a common ancestor. However, in the Archaea branch the sequence was broken into two and ended up in different parts of proteins. Not one known Archaea has a complete DAVTYTEHAK sequence, while most vertebrates have. BastionMonk (talk) 09:11, September 13, 2013 (UTC) In Mary Schweitzer's most recent paper, A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time (2014), she publishes findings on how iron in hemoglobin might be able to preserve proteins and DNA. In the paper, I found this interesting paragraph: "However, just as iron contributes to reduction of antibody reactivity (figure 3; electronic supplementary material, figure S5), it may also confound efforts to sequence biomolecules, by diminishing signals in mass spectrometry via ion suppression or by inhibiting enzymes required for DNA sequencing 81,82. Iron chelation in soft tissue analysis is a technical advance in analysing biomaterials from fossil bone because chelation reduces signal inhibition in many fossil analyses, thus broadening the range of specimens from which molecular data may be obtained." So the same thing that is allowing the DNA and proteins to be preserved is also inhibiting attempts to sequence them. Jurassic Park Treasury (talk) 05:00, February 18, 2014 (UTC) :Great find! Since it fucks up the results of mass spectometry, Iron also inhibits attempts to detect DNA and proteins. That could explain a lot. BastionMonk (talk) 08:26, February 18, 2014 (UTC) ::I personally hope we get more protein sequences this year or the next. I wouldn't be surprised if she found hemoglobin later this year. But I'd welcome any sequence that doesn't have a 100% match to birds or other animals. Not because it implies contamination, but because it doesn't really give us anything new (I'm a bit like Dr. Sorkin, in that I want as much as the genome as possible to be dinosaurian). Jurassic Park Treasury (talk) 03:25, February 19, 2014 (UTC)